What's the difference between Glossy and Glass shaders in Eevee?
From left to right, is Glossy, Glass, and &quot;Shiny&quot;. All 3 have roughness at 0.

Roughness in Principled BSDF determines how &quot;shiny&quot; or &quot;polished&quot; the surface of somthing looks. It bears no effect on the underlying colors.
Glossy is the equivalent of metallic - the color determines the hue of the specular reflection (how much of its own color is reflected back with the light). Default (white) Glossy with roughness 0 is the equivalent of Pure Metal (White basecolor, Roughness = 0, Metallic = 1) on Principled BSDF.
Glass essentially a Glossy shader, but with a transparent BaseColor, and some refraction added which also gives transparent/refracted reflections. It also includes a Fresnel to alter the refractions near the &quot;edge&quot; of objects. It is one of the best ways of replicating glass in Cycles, but has its limitations in EEVEE.